In my application I have a class hierarchy similar to the following one

public sealed interface Animal permits Mammal, Fish {}

public sealed interface Mammal permits Cat, Dog{}

public final class Fish implements Animal {}
public final class Cat implements Mammal {}
public final class Dog implements Mammal {}



class Main{
  public static void main(String[] args){
    new Dog();
    new Cat();
    new Fish();
  }
}

When obfuscating with proguard, it changes the permitted subclasses of the Animal class to [...] Animal permits Fish. I'm suspecting because the Mammal class is not used in my application directly. However, when I try to run the obfuscated application, I get the following error

java.lang.IncompatibleClassChangeError: class fj cannot extend sealed interface ff (java.lang.ClassLoader./.defineClass1./.-2)

Here, fj = Mammal and ff = Animal. So java cannot load the Mammal class because it extends the Animal class and is no longer part of the permitted subclasses.

I'm suspecting that there is a bug in proguard that shrinks the application too much so that it can no longer be run.